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GRE Quantitative Reasoning QUESTION #8169
Question 1

Using the graph of Energy Used per Meter vs. Speed for running and walking: at what speed $s$ (in miles per hour) is the energy used per meter during running exactly twice the energy used per meter during walking? Based on the graph, $s$ lies between:

  • $2.5$ and $3.0$✔️
  • $3.0$ and $3.5$
  • $3.5$ and $4.0$
  • $4.0$ and $4.5$
Correct Answer Explanation

From the Energy vs. Speed graph:

  • The walking curve rises gradually from about 75 J/m at low speed to roughly 150 J/m around 4–5 mph.
  • The running curve starts high (~150 J/m at low speed) and decreases to a minimum around 4 mph, then rises again.

We look for the speed where the running energy is exactly double the walking energy. By reading the graph carefully:

At $s \approx 2.7$ mph: running energy ≈ 150 J/m, walking energy ≈ 75 J/m. Running = 2 × walking. ✓

This speed falls in the range 2.5 to 3.0 mph.